Assembly comprising at least one embedded chip with magnetic head(s)

ABSTRACT

An assembly including at least one chip with an embedded magnetic head. A base and/or a cover includes at least partially a housing in which the at least one chip is embedded. Such an assembly may find particular application to a magnetic recording system.

DESCRIPTION

1. Field of the Invention

This invention involves an assembly including at least one chip with oneor more embedded magnetic heads.

It can be applied in particular to making helicoid recording heads formagnetic tape, for example amateur or professional video recording (homeVDRs or camcorders) or also for computer data recorders which use tapesor disks. There could also be other applications for other types ofrecording heads (linear on tape, on cards, etc.).

The high frequencies which are possible due to the small size of themagnetic heads integrated in thin layers allow for digital recording(for example with the DVC norm for video or DDS for data recording).Tape data recording systems are for mass data storage with the highestcapacities and at the lowest cost. Its computer applications arearchiving of data and backups of hard disks of systems or networks fordistribution of large programs or databases.

2. State of the Art

FIGS. 1 to 3 illustrate the structure of a magnetic head integrated inthin layers which is known from document FR-A-2 747 226. As illustratedin FIG. 1, the head includes two polar pieces 10 ₁, 10 ₂ separated by ahead gap 14, two magnetic branches 16 ₁, 16 ₂ which partly cover thepolar pieces, and a magnetic piece for flux closure 18. This set ofpieces constitutes a magnetic circuit. Around the branches 16 ₁, 16 ₂there are conducting windings 20 ₁, 20 ₂ for reading and/or writing ofthe information written and/or read on the recording medium (not shown).

FIG. 2 shows the complete head with two conducting strips 22 ₁, 22 ₂allowing for access to the conducting windings 20 ₁, 20 ₂ and twoelectrical connection studs 24 ₁, 24 ₂.

The head shown in FIGS. 1 and 2 can be made collectively usingmicro-electronics techniques. To obtain a chip with one or severalmagnetic heads from a card which includes several components or chips,the components must be separated from each other and then the front partof the components next to the polar pieces 10 ₁, 10 ₂ must be machinedto give them the rounded shape needed for proper functioning of thehead. In FIG. 2, the rounded profile is schematically represented by theline 26.

FIG. 3 schematically shows a section view of a head along a line AAwhich goes through one of the conducting strips and one of the branchesof the magnetic circuit as well as the head support. This figure shows asubstrate 30, silicon for example, with one of the polar pieces 10 ₁ or10 ₂, a magnetic branch 16 ₁ or 16 ₂, a conducting strip 22 ₁ or 22 ₂,and the electrical connection studs 24 ₁, 24 ₂. This unit is covered bya superstrate 40, in silicon for example. At the front of the head, thesurface 26, called the bearing surface, has an appropriately roundedshape and a height h which is reduced with respect to the totalthickness of the unit. At the back, the superstrate 40 is disengaged toleave the electrical connection studs 24 ₁, 24 ₂ exposed.

The chip (or chips) is mounted on a base 45, made of brass for example,on one of the sides of which there is a rigid printed circuit 46 whichis electrically linked to the chip by stranded wires 48 ₁, 48 ₂. Theprinted circuit 46 links the head to the electronic circuits whichcontrol writing and/or reading.

The current chips for helicoidal recording are mounted on and glued totheir bases. This gluing is done on the reference plane of the base,machined to give it good evenness, so that the head is perfectlyparallel to the reference plane of the drum to which the base will bescrewed. The position can be adjusted with the screw.

The current assemblies are poorly adapted to miniaturisation of heads,because the mechanical resistance of the chip on a single gluing side ofthe base is not sufficient when the size of the head becomes very small.In the future, integrated heads will progressively replacemicro-machined heads, because they are much better suited to increasingthe density of information. The heads will thus be smaller and smaller.The base must be adapted as a consequence. Gluing the chip to a singleplane is not sufficient because it does not ensure good mechanicalresistance of the head when it is working.

The Japanese patent application 60-020311 describes a support-magnetichead assembly in which a chip is introduced in a groove made at thefront of the base.

Japanese patent application 07-296325 describes a support-magnetic headassembly in which the head abuts the bottom of a housing.

SUMMARY OF THE INVENTION

This invention aims to improve the resistance of the head (or heads) inits (their) support.

To this end, the invention proposes a chip(s)-base assemblycharacterised in that it includes a base and a cover over at least partof the chip(s), the chip(s) being embedded in a housing between the baseand the cover. This embedded housing can be located either completelywithin the base, or completely within the cover, or partially within thebase and partially within the cover.

In the case of a single chip, the chip having two lateral sides, anupper side, a lower side and a rear side, at least one of these sidescan be glued to the wall of the embedded housing. At least two sides canpossibly be glued. The lower side of the chip can also be glued to thebottom of the housing, keeping in mind that, without particularprecautions, the thickness of the glue could affect the positioning ofthe chip. Thus glued and embedded, the chip is held solidly on the base.

The chip can also, in certain cases, be glued to the cover. This covercan be a hollow piece fitting against the base.

The chip can include one or several magnetic heads. There can also beseveral chips on the base, each embedded in a housing (or in the samehousing), ensuring its relative positioning with respect to the othersboth laterally and in terms of depth.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of theattendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

FIG. 1, already described, shows a magnetic head according to the stateof the art;

FIG. 2, already described, shows, in an overhead view, a magnetic headwith its electric connection studs;

FIG. 3, already described, shows the same head in a cross-section andassembled on its base;

FIG. 4 is an overhead view of an assembly according to the invention;

FIG. 5 is a side view of the assembly according to the invention;

FIG. 6 shows a section of the assembly with a cover;

FIG. 7 illustrates a particular embodiment of the base;

FIG. 8 is an overhead view showing a rigid printed circuit allowing formaking of a cover and establishing an electrical connection;

FIG. 9 is a cross section of the chip-base-printed circuit assembly;

FIG. 10 shows this assembly in an overhead view;

FIGS. 11a, 11 b and 11 c show a rigid printed circuit allowing formaking of a cover, (11 a in overhead view, 11 b profile with base withdeep embedding, 11 c variant with notch);

FIG. 12 is an overhead view of a base with two chips with single headsembedded at controlled distances.

DESCRIPTION OF PARTICULAR EMBODIMENTS

FIG. 4 shows a chip 50 which is assumed to contain two magnetic heads.The chip thus includes, on its rear edge, two double electricalconnection studs, P₁, P₂. There is also a base 60 with an upper side 61,a front side 63 and a rear side 64. The side 61 acts as a referenceplane. It can be machined to adapt the position of the head 50 to thedesired height. The chip 50 is embedded in the base 60, in a housing 65provided at the front of the base.

FIG. 5 shows the same elements with the same numerical references but ina side view. The connection wires 67 are also seen.

In the variant illustrated, the chip is embedded in the housing 65 overabout half of its height. Its two lateral sides are thus in contact withthe lateral walls of the housing, over half of their height. One and/orthe other of these sides can be glued to the walls of the housing.

FIG. 6 illustrates a variant in which the cover 88 fits against the base60. An embedded housing 65′ can be machined in the cover 88. The chip 50is then partially embedded in the base (housing 65) and partially in thecover 88 (housing 65′). But the chip can also be embedded only in thecover.

This invention can be combined with the invention described and claimedin the French patent application entitled “Assembly for chip(s) withmagnetic head(s) and manufacturing process” submitted on Aug. 21, 1998.This combination is illustrated in FIGS. 7 to 11.

FIG. 7 shows the particular shape of the base 60 with the enlarged rearpart, a hole 66 and two notches 67, 68 located in the middle part.

FIG. 8 shows a rigid printed circuit 70 with conducting tracks 76, 77arranged on the lower side of the circuit, these tracks having frontends 76′, 77′ placed so that they are above the connection studs P1, P2of the chip when the printed circuit is in place. At the rear ends ofthe conducting tracks 76 and 77, there are two pairs of connection studsP′₁, P′₂ which can connect with an electronic circuit (not shown).

The rigid printed circuit 70 also includes an opening 80 which isessentially rectangular and bordered by two lateral strips 82, 84. Thisopening 80 is sufficiently wide so that the chip-base unit in FIG. 7 canbe put into it. The lateral strips 82, 84 of the printed circuit gothrough the notches 67, 68 in the base. The rigid printed circuitcontains a hole 90, of the same diameter as the hole 66 made in the baseto allow for insertion of the means of attachment. The rigid printedcircuit also has, at the font, a rigid piece 88 which acts as a coverfor the chip. It can be glued to the chip and/or to the base.

This cover reduces the risks of vibration, a valuable feature for drumswhich turn rapidly, for example at 9000 rotations/minute.

FIGS. 9 and 10 show the assembly obtained, in side view and overheadview respectively. The references indicate the same elements as in FIGS.7 and 8. FIG. 9 shows, in particular, that the printed circuit 70 hasits upper side 71 which comes against the lower side 62 of the base 60and its lower side 72 which comes into contact with the connection studsof the chip 50. FIG. 9 also shows an attachment hole 90 which allows forassembly of the head on a drum by means of a screw.

FIG. 10 shows the same elements and the lateral sides 82 and 84 usingthe notches made in the base.

The positioning of the cover on the chip-base unit can be doneautomatically using a video camera and a shape recognition program.

FIG. 11a shows, in an overhead view, an example of a printed circuitwith a rigid cover with printed connection tracks and a central hole 80for the base.

The breaks or edges 93 and 94 show that this cover is made on twolevels, visible on FIG. 11b: a first level located on the base, partlycovering the chip(s) 50 and electrically connecting the studs 76′, 77′of the tracks 76, 77 to the studs P₁, P₂ of the chips, a second levellocated under the base equipped with studs P′₁, P′₂ to connect thisassembly to the signal processing electronics. FIG. 11b shows this coverpositioned on its base in a side view. The base is shown with deepembedding of the chip 50.

FIG. 11c shows a variant of the rigid cover with a notch instead of thecentral hole, allowing for a side assembly and an adaptation to bases ofdifferent shapes.

FIG. 12 shows an example of a base with two embedded chips withindividual heads. The distance “d” between the chips can be preciselydefined by the position of the housings in which the chips will beembedded. The height of the heads (position on the axis perpendicular tothe plane of FIG. 12) can be defined either by the depth of thehousings, or by the position of the polar pieces of the heads in thechip.

There could also be bases with several housings for chips with one orseveral heads per chip, equipped with a cover which could electricallyconnect the heads to the printed circuit of the assembly.

What is claimed is:
 1. An assembly comprising: at least one chip with atleast one magnetic head; a base; a cover over at least part of the atleast one chip, the at least one chip being recessed in a housingbetween the base and the cover; wherein the cover is composed of a frontpart of a printed circuit with a lower side covered with conductingtracks in contact with connection studs of the at least one chip locatedat a rear of the chip.
 2. An assembly according to claim 1, in which theembedded housing is located either entirely in the base or entirely inthe cover.
 3. An assembly according to claim 1, in which the embeddedhousing is located partially in the base and partially in the cover. 4.An assembly according to claim 1, in which at least one of the sides ofthe chip is glued to the walls of the housing.
 5. An assembly accordingto claim 1, in which the cover fits onto the base.
 6. An assemblyaccording to claim 1, in which plural chips are embedded in one orplural housings at a precise position which defines their separationwith respect to neighboring chips, their height being defined by thedepth of the one or plural housings.
 7. An assembly comprising: at leastone chip with at least one magnetic head and at least one connectionstud; a base; a cover over at least part of the at least one chip, theat least one chip being embedded over about one half of its height in ahousing between the base and the cover.
 8. An assembly according toclaim 7, in which the embedded housing is located either entirely in thebase or entirely in the cover.
 9. An assembly according to claim 7, inwhich the embedded housing is located partially in the base andpartially in the cover.
 10. An assembly according to claim 7, in whichthe at least one of the sides of the chip is glued to the walls of thehousing.
 11. An assembly according to claim 7, in which the cover fitsonto the base.
 12. An assembly according to claim 7, wherein the coveris composed of a front part of a printed circuit with a lower sidecovered with conducting tracks in contact with connection studs of theat least one chip located at a rear of the chip.
 13. An assemblyaccording to claim 7, in which plural chips are embedded in one orplural housings at a precise position which defines their separationwith respect to neighboring chips, their height being defined by thedepth of the one or plural housings.